They put Christmas thing the tree.[ ]
A. on
B. in
C. to
D. at
答案：A
证券投资基金的出现和发展，能有效地改善证券市场的（）结构。
A.投资者
B.风险
C.年龄
D.品种
—London or Paris?
—What are you talking about?
—We are talking about _____ to travel.[ ]
A. how
B. where
C. who
